Data Structures & Algorithms
The core computer-science toolkit for problem solving and interviews.
Beginner
Start here. No background needed beyond school maths.
Book
Beginner
↗ External site
Algorithms, 4th Edition (booksite)
Free lectures, code and exercises for the classic Princeton text on sorting, searching, graphs and strings, in Java.
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Document
Beginner
↗ External site
Data Structure Visualizations
Step-by-step animations of stacks, trees, heaps, hash tables and sorting that you can control with your own input.
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Document
Beginner
↗ External site
VisuAlgo
Animated visualisations of data structures and algorithms that you can step through, with quizzes to test yourself.
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